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Abstract:

A method can include receiving at a cluster head, a multicast/broadcast
packet from a base station. The method can also include monitoring, at
the cluster head, to detect whether any members of a cluster of the
cluster head responds to the multicast/broadcast packet with a negative
acknowledgment directed to the cluster head. The method can further
include, when a result of the monitoring is no detection of any negative
acknowledgments, and the cluster head successfully received the
multicast/broadcast packet, sending, by the cluster head, a general
acknowledgment of the multicast/broadcast packet to the base station.

Claims:

1-23. (canceled)

24. A method, comprising: receiving at a cluster head, a
multicast/broadcast packet from a base station; monitoring, at the
cluster head, to detect whether any members of a cluster of the cluster
head responds to the multicast/broadcast packet with a negative
acknowledgment directed to the cluster head; and sending, by the cluster
head, a general acknowledgment feedback of the packet to the base
station.

25. The method according to claim 24, further comprising: when a result
of the monitoring is no detection of any negative acknowledgments, and
the cluster head successfully received the multicast/broadcast packet,
sending, by the cluster head, a general acknowledgment of the
multicast/broadcast packet to the base station.

26. The method according to claim 24, further comprising: when the result
of the monitoring is detection of at least one negative acknowledgment,
and the cluster head successfully received the multicast/broadcast
packet, sending, by the cluster head, a specific acknowledgment of the
multicast/broadcast packet to the base station and re-transmitting the
packet to the cluster member(s) that did not receive the packet
correctly.

27. The method of according to claim 24, further comprising: when a
result of the monitoring is detection of at least one of the cluster
members that has not provided a negative acknowledgment, and the cluster
head has unsuccessfully received the multicast/broadcast packet, sending,
by the cluster head, a specific negative acknowledgment of the
multicast/broadcast packet to the base station.

28. The method according to claim 24, further comprising: when a result
of the monitoring is detection of all cluster members providing negative
acknowledgment, and the cluster head has unsuccessfully received the
multi/broadcast packet, sending, by the cluster head, a general negative
acknowledgment of the multicast/broadcast packet to the base station.

29. A method, comprising: receiving, at a cluster member, a
multicast/broadcast packet from a base station; monitoring, at the
cluster member, to determine whether another cluster member responds to a
cluster head with a negative acknowledgment; monitoring, at the cluster
member, to determine what kind of acknowledgment the cluster head uses to
respond to the base station, wherein the kind is one kind selected from a
general affirmative acknowledgment, a general negative acknowledgment, a
specific affirmative acknowledgment, or a specific negative
acknowledgment.

30. The method according to claim 29, further comprising: when the
cluster head did not successfully receive the packet as indicated by a
specific negative acknowledgment and the cluster member successfully
received the packet, determining whether to send the multicast/broadcast
packet to the cluster head and other cluster member(s) who have not
received the packet correctly based on predetermined rules.

31. The method according to claim 29, wherein the predetermined rules
include an order of priority among members of a cluster, and wherein the
cluster member determines whether to send the multicast/broadcast packet
based on the priority of the cluster member relative to at least one
other member of the cluster.

32. An apparatus, comprising: at least one memory including computer
program code; and at least one processor, wherein the at least one memory
and the computer program code are configured to, with the at least one
processor, cause the apparatus at least to receive at a cluster head, a
multicast/broadcast packet from a base station; monitor to detect whether
any members of a cluster of the cluster head responds to the
multicast/broadcast packet with a negative acknowledgment directed to the
cluster head; and send a general acknowledgment feedback of the packet to
the base station.

33. The apparatus according to claim 32, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to, when a result of the
monitoring is no detection of any negative acknowledgments, and the
cluster head successfully received the multicast/broadcast packet, send,
by the cluster head, a general acknowledgment of the multicast/broadcast
packet to the base station.

34. The apparatus according to claim 32, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to, when a result of the
monitoring is detection of at least one negative acknowledgment, and the
cluster head successfully received the multicast/broadcast packet, send,
by the cluster head, a specific acknowledgment of the multicast/broadcast
packet to the base station and to re-transmit the packet to the cluster
member(s) that did not receive the packet correctly.

35. The apparatus according to claim 32, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to, when a result of the
monitoring is detection of at least one of the cluster members that has
not provided a negative acknowledgment, and the cluster head has
unsuccessfully received the multicast/broadcast packet, send, by the
cluster head, a specific negative acknowledgment of the
multicast/broadcast packet to the base station.

36. The apparatus according to claim 32, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to, when a result of the
monitoring is detection of all cluster members providing negative
acknowledgment, and the cluster head has unsuccessfully received the
multicast/broadcast packet, send, by the cluster head, a general negative
acknowledgment of the multicast/broadcast packet to the base station.

37. An apparatus, comprising: at least one memory including computer
program code; and at least one processor, wherein the at least one memory
and the computer program code are configured to, with the at least one
processor, cause the apparatus at least to send, by a base station, a
multicast/broadcast packet to a cluster including a cluster head and
cluster member(s); store in a storage buffer the multicast/broadcast
packet while awaiting an acknowledgment of the multicast/broadcast
packet; and release the storage buffer upon receiving any acknowledgment
of the multicast/broadcast packet except a general negative
acknowledgment.

38. The apparatus according to claim 37, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to send a subsequent
multicast/broadcast packet with a predetermined delay when the
acknowledgment is either a specific negative acknowledgment or a specific
affirmative acknowledgment.

39. The apparatus according to claim 37, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to re-send the
multicast/broadcast packet upon receiving a general negative
acknowledgment.

40. An apparatus, comprising: at least one memory including computer
program code; and at least one processor, wherein the at least one memory
and the computer program code are configured to, with the at least one
processor, cause the apparatus at least to receive, at a cluster member,
a multicast/broadcast packet from a base station; monitor to determine
whether another cluster member responds to a cluster head with a negative
acknowledgment; monitor to determine what kind of acknowledgment the
cluster head uses to respond to the base station, wherein the kind is one
kind selected from a general affirmative acknowledgment, a general
negative acknowledgment, a specific affirmative acknowledgment, or a
specific negative acknowledgment.

41. The apparatus according to claim 40, wherein the at least one memory
and the computer program code are also configured to, with the at least
one processor, cause the apparatus at least to, when the cluster head did
not successfully receive the packet as indicated by a specific negative
acknowledgment and the cluster member successfully received the packet,
determine whether to send the multicast/broadcast packet to the cluster
head and other cluster member(s) based on predetermined rules.

42. The apparatus according to claim 40, wherein the predetermined rules
include an order of priority among members of a cluster, and wherein the
cluster member determines whether to send the multicast/broadcast packet
based on the priority of the cluster member relative to at least one
other member of the cluster.

Description:

BACKGROUND

[0001] 1. Field

[0002] Device to device (D2D) communication can employ various
acknowledgment schemes. In particular, D2D communications can assist the
use of acknowledgment, by a cluster, of a multicast message sent to the
cluster.

[0003] 2. Description of the Related Art

[0004] Multicast services are becoming more and more popular with the
development of cellular wireless networks (e.g. long term evolution (L
1E) networks), where data is transmitted to multiple recipients by an
evolved Node B (eNodeB) or similar base station device. By utilizing the
shared nature of wireless medium, multicast service can be realized with
a high efficiency. In order to support reliable packet delivery in
multicast service, hybrid automatic repeat request (HARQ) protocol can be
incorporated into the packet multicasting process, i.e. each device in
the recipient cluster will feedback an acknowledgement and negative
acknowledgement (ACK/NACK) message for each of the multicast packets; and
a packet will be retransmitted if a NACK message is reported by the
service recipient. Typically, the HARQ acknowledgement is packet-wise,
i.e., every packet recipient reports its own acknowledgment to the
control node in universal terrestrial radio access network (UTRAN) and
enhanced UTRAN (E-UTRAN), the control node retransmits the packet
according to the received HARQ acknowledgement.

[0005] For multicasting service with a device-to-device (D2D) cluster, the
HARQ acknowledgement for requesting the retransmission or new
transmission from eNodeB is one of the signaling elements to be
considered. Because a cluster of devices may need to feed back the HARQ
acknowledgement, optimization of HARQ feedback signaling for a cluster of
devices can help to control the efficiency of uplink control signaling
and minimize its impact on system efficiency.

SUMMARY

[0006] In certain embodiments, the present invention is a method. The
method can include receiving at a cluster head, a multicast/broadcast
packet from a base station. The method can also include monitoring, at
the cluster head, to detect whether any members of a cluster of the
cluster head responds to the multicast/broadcast packet with a negative
acknowledgment directed to the cluster head. The method can further
include, when a result of the monitoring is no detection of any negative
acknowledgments, and the cluster head successfully received the
multicast/broadcast packet, sending, by the cluster head, a general
acknowledgment of the multicast/broadcast packet to the base station.

[0007] In further embodiments, the present invention is also a method. The
method can include sending, by a base station, a multicast/broadcast
packet to a cluster including a cluster head and cluster member(s). The
method can also include storing, in a storage buffer at the base station,
the multicast/broadcast packet while awaiting an acknowledgment of the
multicast/broadcast packet. The method can further include releasing, by
the base station, the storage buffer upon receiving any acknowledgment of
the multicast/broadcast packet except a general negative acknowledgment.

[0008] The present invention is, in additional embodiments, a method. The
method can include receiving, at a cluster member, a multicast/broadcast
packet from a base station. The method also can include monitoring, at
the cluster member, to determine whether another cluster member responds
to a cluster head with a negative acknowledgment. The method can further
include monitoring, at the cluster member, to determine what kind of
acknowledgment the cluster head uses to respond to the base station,
wherein the kind is one kind selected from a general affirmative
acknowledgment, a general negative acknowledgment, a specific affirmative
acknowledgment, or a specific negative acknowledgment.

[0009] A computer-readable medium encoded with instructions that, when
executed in hardware, perform a process is the invention in certain
embodiments. The process can be any of the above-discussed methods.

[0010] An apparatus is the invention in certain embodiments. The apparatus
can include at least one memory including computer program code and at
least one processor. The at least one memory and the computer program
code can be configured to, with the at least one processor, cause the
apparatus at least to receive at a cluster head, a multicast/broadcast
packet from a base station. The at least one memory and the computer
program code can also be configured to, with the at least one processor,
cause the apparatus at least to monitor to detect whether any members of
a cluster of the cluster head responds to the multicast/broadcast packet
with a negative acknowledgment directed to the cluster head. The at least
one memory and the computer program code can further be configured to,
with the at least one processor, cause the apparatus at least to, when a
result of the monitoring is no detection of any negative acknowledgments,
and the cluster head successfully received the multicast/broadcast
packet, send, by the cluster head, a general acknowledgment of the
multicast/broadcast packet to the base station.

[0011] Certain further embodiments of the invention are also an apparatus.
The apparatus includes at least one memory including computer program
code and at least one processor. The at least one memory and the computer
program code can be configured to, with the at least one processor, cause
the apparatus at least to send, by a base station, a multicast/broadcast
packet to a cluster including a cluster head and cluster member(s). The
at least one memory and the computer program code can also be configured
to, with the at least one processor, cause the apparatus at least to
store in a storage buffer the multicast/broadcast packet while awaiting
an acknowledgment of the multicast/broadcast packet. The at least one
memory and the computer program code can further be configured to, with
the at least one processor, cause the apparatus at least to release the
storage buffer upon receiving any acknowledgment of the
multicast/broadcast packet except a general negative acknowledgment.

[0012] Certain additional embodiments of the present invention can include
an apparatus. The apparatus can include at least one memory including
computer program code and at least one processor. The at least one memory
and the computer program code can be configured to, with the at least one
processor, cause the apparatus at least to receive, at a cluster member,
a multicast/broadcast packet from a base station. The at least one memory
and the computer program code can also be configured to, with the at
least one processor, cause the apparatus at least to monitor to determine
whether another cluster member responds to a cluster head with a negative
acknowledgment. The at least one memory and the computer program code can
further be configured to, with the at least one processor, cause the
apparatus at least to monitor to determine what kind of acknowledgment
the cluster head uses to respond to the base station, wherein the kind is
one kind selected from a general affirmative acknowledgment, a general
negative acknowledgment, a specific affirmative acknowledgment, or a
specific negative acknowledgment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For proper understanding of the invention, reference should be made
to the accompanying drawings, wherein:

[0020] FIG. 7 illustrates a method according to an embodiment of the
present invention.

[0021]FIG. 8 illustrates a method according to an embodiment of the
present invention.

[0022]FIG. 9 illustrates a method according to an embodiment of the
present invention.

[0023]FIG. 10 illustrates a system according to certain embodiments of
the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0024] Certain ACK/NACK feedback schemes for eNodeB controlled D2D cluster
communications with a cluster head can be configured to save cellular
system overhead and reduce retransmission latency. Such schemes can be
applied to broadcasting environment with receiving status feedback and
cluster head among all the devices in question.

[0025] In eNodeB controlled D2D cluster communications as illustrated in
FIG. 1, a cluster of devices receive the same data packet via eNodeB
multicasting, some of the devices receive the packet successfully while
others fail. In the worst case, none of them receives the packet
successfully. In order to guarantee received packets correctly, ACK/NACK,
modulation coding scheme (MCS) assignment and channel quality indicator
(CQI) of D2D links etc. feedback is conventionally thought to be
inevitable. Such feedback implies significant signaling overhead and
power consumption for device, consequently leads to cellular system
capacity and throughput reduction.

[0026] As illustrated in FIG. 2, in a straightforward scheme, eNodeB sends
the packets to a cooperating device and a destination device (a recipient
cluster). The co-operating device can be the same as the D2D cluster head
and the destination device can be the same as the D2D device within the
cluster. If the packet as received contains an error and if the link
within the cluster is better than cellular link, it may be more efficient
to re-transmit among the cluster devices via a recipient cluster link.
One example straightforward signaling and retransmission mechanism is as
follows: the cooperating device and destination device send an ACK/NACK
message to feedback receiving status to eNodeB respectively via a
cellular link. Then the cooperating device with the correct packet
reception can re-transmit the packet to destination device via the
recipient cluster link.

[0027] Using this approach, if we assume there are N destination UEs and 1
cooperating UE, N+1 bits HARQ acknowledgement feedback signaling is
needed via the cellular uplink.

[0028] The another straightforward way for the HARQ feedback signaling is
that all the destination UEs send the HARQ acknowledgement to the
co-operating UE and co-operating UE forwards all the HARQ acknowledgement
feedback to the eNodeB. By that way, N bits HARQ acknowledgement feedback
is needed within the cluster and N+1 bits HARQ acknowledgement feedback
is needed via the cellular uplink. On the other hand, eNodeB may need to
inform which UE is responsible for the retransmission in the cellular
downlink.

[0029] In view of the discussion above, it can be seen that it is a big
challenge to optimize signaling overhead, reduce power consumption as
much as possible and still provide reliable information to eNodeB.
Certain embodiments of the present invention aim to provide an efficient
ACK/NACK feedback scheme for eNodeB controlled D2D cluster communications
with cluster head to save cellular signaling overhead and reduce cellular
power consumption while guaranteeing system reliability.

[0030] More specifically, certain embodiments of the present invention aim
to provide an efficient ACK/NACK feedback scheme for eNB
multicast/broadcast for eNB controlled D2D cluster communications with
cluster head to save cellular signaling overhead, reduce cellular power
consumption and guarantee system reliability. Such ends may be
accomplished, in certain embodiments by the cluster head categorizing
decoding results (ACK/NACK) for the cluster into 4 cases, and sending the
cluster's receiving status via cellular link. Additionally, reliance may
be placed on the eNodeB and all the cluster devices listening to the
cluster head's response.

[0031] The four cases may be as shown in the following example:

[0032] Case 1 All_NACK: None of the devices in the D2D cluster receives
packet successfully. In response to this case, the eNB can retransmit the
same packet.

[0033] Case 2 All_ACK: All devices in the D2D cluster (include the head
itself) receive the packet successfully. In response to this case, the
eNB can multicast a new packet.

[0034] Case 3 Self_ACK: The D2D cluster head itself receives the packet
successfully, and at least one cluster device has a packet error. The D2D
cluster head can retransmit the same packet to the cluster member, and
the eNB can remove the packet from its storage buffer.

[0035] Case 4 Self_NACK: The D2D cluster head itself receives the packet
with a packet error, but at least one cluster device receives the correct
packet successfully. The D2D cluster device with highest priority order
can retransmit the same packet to the cluster head. Optionally, the
cluster device can simultaneously retransmit the same packet to one or
more of the other cluster devices. Alternatively, once the cluster head
has received the packet, the cluster head.

[0036] In case 4, there are several ways in which the retransmission of
the packet can proceed. For example, the cluster head may specifically
request retransmission by a cluster member which successfully received
the packet. The request may be for a multicast of the packet to all
NACKed members of the cluster including the cluster head, or a simple
transmission to the cluster head for subsequent distribution to the
cluster members.

[0037] Alternatively, a cluster member that successfully received the
packet can be automatically selected based on predetermined rules. The
predetermined rules can include a pre-ordering for D2D cluster devices,
such as discussed below.

[0038] For example, all the D2D cluster devices can be pre-ordered based
on any kind of decision criteria. One example of the decision criteria
can be a MAC address of the D2D cluster device, wherein the pre-order may
be in ascending order of MAC address. This would require that each D2D
device know the MAC addresses of the other devices in the cluster. The
pre-order of the device can be assigned to each device either implicitly
or explicitly. All the devices with packet error can send a NACK to the
cluster head and the rest of the devices, which received the packet
correctly can listen.

[0039] By pre-ordering in case 4 where the packet will be retransmitted
among the cluster, the cluster devices can decide by themselves who
(e.g., the highest-order device with correct packet reception) will be
responsible to retransmit the packet within the cluster. The
retransmitting cluster device assignment signaling could be avoided by
such an arrangement.

[0040] Certain embodiments of the present invention can utilize less
signaling overhead and have lower power consumption than previous
approaches.

[0041] An ACK/NACK feedback scheme for eNodeB controlled D2D cluster
communications as an example implementation of the approach outlined
above is presented below. A general assumption for the example
implementation is that the D2D cluster head manages/maintains the devices
within the cluster in semi-static manner.

[0042] Based on such an assumption, the scheme can include two-bit HARQ
acknowledgment feedback via a cellular link. eNodeB while all cluster
devices listen. The two-bit feedback can encode four cases, which have
been, in this example, organized differently than in the preceding
example:

[0043] Case 1 All_ACK: All devices in the D2D cluster (including the
cluster head itself) receive the packet successfully. In this case, the
eNodeB (or other base station element) can multicast a new packet.

[0044] Case 2 All_NACK: None of the devices in the D2D cluster (including
the cluster head) receives the packet successfully. In this case, the
eNodeB can re-transmit the same packet.

[0045] Case 3 Self_ACK: The D2D cluster head itself receives the packet
successfully, and at least one cluster device (other than the cluster
head) receives the packet with a packet error. The D2D cluster head can
re-transmit the same packet to the one or more cluster devices that
experienced a packet error.

[0046] Case 4 Self_NACK: The D2D cluster head itself receives the packet
with a packet error, but at least one cluster device receives the packet
successfully. The D2D cluster device with the highest priority order can
re-transmit the same packet.

[0047] The pre-ordering for D2D cluster devices can be based on any kind
of decision criteria, as noted above. By pre-ordering in case 4 where the
packet is to be re-transmitted among the cluster (not by the cluster
head), the cluster devices can decide by themselves who (e.g., the
highest-order device with correct packet reception) will be responsible
to re-transmit the packet within the cluster. By pre-ordering, the
re-transmitting cluster device assignment signaling could be avoided for
each retransmission.

[0048] Based on the above scenario assumptions and HARQ acknowledgment
feedback scheme via D2D and cellular link respectively, the overall
procedure of the proposed HARQ acknowledgement feedback for D2D cluster
communication can be implemented as set forth below:

[0049] All the D2D cluster devices can be pre-ordered. Then, an eNodeB can
multicast the data packet to the D2D cluster. Each cluster device and
cluster head decodes the received packet. If decoding is successful, the
decision is ACK; otherwise, the decision is NACK. If the decision is NACK
for a particular cluster device, the cluster device with packet error
sends NACK via D2D link. The cluster head and cluster devices with
decision ACK, i.e. with a correctly received packet, listen. The cluster
head can categorize the overall decoding result of all the devices into
one of the four cases above, and can send a message indicative of the
overall receiving status representing the cluster via cellular link. The
eNodeB and all the cluster devices can listen to the cluster head's
message.

[0051] Case 1 All_ACK. As noted above, in this case, all the devices in
the D2D cluster receive the packet successfully, as illustrated in FIG.
3. No cluster device sends NACK to the cluster head, but instead each of
the cluster devices listens. As the cluster head does not receive
anything from the other cluster devices in a pre-defined time interval,
the cluster head sends an All-ACK via a cellular link to the eNodeB. The
eNodeB and the cluster devices listen. Then, the eNodeB can release the
storage buffer and multicast the new packet. The cluster head and the
other D2D devices can receive the new packet via the cellular link.

[0052] Case 2 All_NACK. In this case, none of the D2D cluster devices,
including the cluster head, receives the packet successfully, as
illustrated in FIG. 4. The cluster devices with a packet error send a
NACK message to the cluster head and the cluster head listens. The
cluster head then sends an All_NACK via a cellular link to the eNodeB.
The eNodeB and the cluster devices listen. Of course, it is not
particularly necessary for the cluster devices to listen in this case,
since none of the cluster devices would be able to retransmit the packet,
regardless of whether or not the cluster head received the packet. Then
the eNodeB can multicast/re-transmit the same packet. The cluster head
and other cluster devices receive the re-transmitted packet via cellular
link.

[0053] Case 3 Self_ACK. In this case, the D2D cluster head receives the
packet successfully, but at least one cluster device receives the packet
unsuccessfully, as illustrated in FIG. 5. The cluster devices which have
received the packet with a packet error send a NACK via the D2D link.
Cluster devices that received the packet successfully, as well as the
cluster head listen. Then the cluster head sends a Self_ACK via a
cellular link. The eNodeB and all the cluster devices listen. In
response, the eNodeB releases the storage buffer and permits the cluster
devices to handle the retransmission. The cluster head can retransmit the
packet and the NACKed devices can listen via the D2D link.

[0054] After decoding the retransmitted packet from the cluster head, the
NACKed UE can send the receiving status to cluster head as usual. The
cluster head can send either a Self_ACK or an All_ACK to the eNB based on
the receiving status from the cluster members. This can be repeated until
a predetermined maximum number of retransmissions is reached or until
All_ACK is achieved. The eNB can decide to send a new packet if ALL_ACK
was sent or await retransmission within the cluster if Self_ACK is
received.

[0055] Case 4 Self_NACK. In this case, the D2D cluster head does not
receive packet successfully, but at least one cluster device receives the
packet successfully, as illustrated in FIG. 6. The cluster devices with
packet error can send a NACK via the D2D link. Cluster devices with the
correct packet, as well as the cluster head, listen. Then, the cluster
head can send a Self_NACK via the cellular link. The eNodeB and all the
cluster devices can listen. In response, the eNodeB can release the
storage buffer and let the cluster devices handle the retransmission. The
cluster device with the correct packet and the highest order can
retransmit the packet, and the NACKed devices (and cluster devices that
have the correct packet but a lower order) can listen via D2D link.

[0056] After decoding the retransmitted packet, the NACKed UE can send the
receiving status to the cluster head as usual. The cluster head can send
either a Self_ACK, All_ACK, or Self_NACK to the eNB based on the
receiving status from the cluster members. This process can be repeated
until a maximum number of retransmissions is reached or until All_ACK is
achieved. The eNB can decide to send a new packet if ALL_ACK is sent or
to await retransmission within the cluster if Self_ACK/Self_NACK.

[0057] As an example, in Table 2 there are N=5 UEs and 1 cluster head. The
"ACK" UEs (UE2, 3,and 5) can be monitoring while the NACKed UEs (UE1 and
4) are sending the NACK to cluster head. By code division multiplexing
(CDM) techniques as one of the options, the UE specific NACK can be
distinguished at the receiving UE according to the UE specific code
sequence information. Therefore, UE2 can deduce by itself that it is to
retransmit the packet via the D2D link according to the pre-ordering of
the devices.

[0058] As long as there is a cluster head among the devices in question,
the above-described method can be applied to the receiving status
feedback broadcasting environment. Thus, a system can be employed that
may provide various benefits relative to previous implementations of
status feedback in a broadcasting environment.

[0059] For example, such a method and system may result in less cellular
UL HARQ signaling overhead. Thus, such a method and system may enable a
more efficient utilization of the available bandwidth.

[0060] As illustrated in Table 3 (below), N+1 can be the number of cluster
devices, including a cluster head. A conventional scheme always requires
N+1 bits for cellular uplink signaling. In contrast, in certain
embodiments of the present invention, the scheme requires only 2 bits to
feedback the overall receiving status of the cluster head and all the
cluster devices so that the cellular uplink signaling can be reduced
significantly, especially as the number of cluster devices gets large.

[0061] Additionally, certain embodiments of the present invention may
reduce power consumption of the devices. Although N-bit HARQ
acknowledgment via the D2D link may still be needed, because the D2D link
may be relatively better than cellular link, the D2D link may consume
much less transmission power and resources. Indeed, lower protection may
be needed for D2D signaling. Furthermore, in certain embodiments, only
NACKed cluster devices send NACK signals.

[0062] Moreover, certain embodiments of the present invention can save
eNodeB buffer storage. For example, certain embodiments of the ACK/NACK
feedback scheme can enable intra-cluster retransmission whenever one
cluster device or the cluster head receives the packet successfully.
Thus, the eNodeB can release the storage buffer for the original packet
as early as possible.

[0063] Furthermore, in certain embodiments of the present invention there
is no need to engage in re-transmitting cluster device assignment
signaling for each retransmission. By pre-ordering, the re-transmitting
cluster device assignment signaling can be avoided for each
retransmission.

[0064] When all the cluster devices are pre-ordered, based on any kind of
decision criteria, a common decision mechanism can be defined in advance.
The decision criteria could be connected with the code used for providing
the code multiplexed NACK response. In other examples, cluster devices
could be ordered based on intra-cluster device identification (ID), or
based on order of joining the cluster, etc. While such a mechanism may
require planning in advance, it does not necessarily require extra
signaling, or, at least, may not necessarily require extra signaling
every time the mechanism is employed.

[0065] FIG. 7 illustrates a method according to an embodiment of the
present invention. As shown in FIG. 7, the method can include receiving
710 at a cluster head, either successfully or unsuccessfully, a
multicast/broadcast packet from a base station. The term "receive" here
does not require a successful reception, without packet errors, but also
includes a reception in which the packet cannot be decoded. The method
can also include monitoring 720, at the cluster head, to detect whether
any members of a cluster of the cluster head responds to the
multicast/broadcast packet with a negative acknowledgment (for example, a
NACK) directed to the cluster head. The method of FIG. 7 further
includes, when a result of the monitoring is no detection of any negative
acknowledgments, and the cluster head successfully received the
multicast/broadcast packet, sending 730, by the cluster head, a general
acknowledgment of the multicast/broadcast packet to the base station. The
general acknowledgment can be an ACK_ALL message.

[0066] The method can further include, when the result of the monitoring
is detection of at least one negative acknowledgment, and the cluster
head successfully received the multicast/broadcast packet, sending 740,
by the cluster head, a specific acknowledgment of the multicast/broadcast
packet to the base station and re-transmitting the packet to the cluster
member(s) that did not receive the packet correctly. The specific
acknowledgment can be a Self_ACK message. The method can also include,
when the result of the monitoring is detection of at least one of the
cluster members that has not provided a negative acknowledgment, and the
cluster head has unsuccessfully received the multicast/broadcast packet,
sending 750, by the cluster head, a specific negative acknowledgment of,
the multicast/broadcast packet to the base station. The specific negative
acknowledgment can be a Self_NACK message. The method can additionally
include, when the result of the monitoring is detection of all cluster
members providing negative acknowledgment, and the cluster head has
unsuccessfully received the multicast/broadcast packet, sending 760, by
the cluster head, a general negative acknowledgment of the
multicast/broadcast packet to the base station. The general negative
acknowledgment can be a NACK_all message.

[0067]FIG. 8 illustrates a method according to an embodiment of the
present invention. As shown in FIG. 8, the method includes sending 810,
by a base station, a multicast/broadcast packet to a cluster including a
cluster head and cluster member(s). The method also includes storing 820,
in a storage buffer at the base station, the multicast/broadcast packet
while awaiting an acknowledgment of the multicast/broadcast packet. Upon
receiving 825 an acknowledgment, the method further includes releasing
830, by the base station, the storage buffer upon receiving any
acknowledgment of the multicast/broadcast packet except a general
negative acknowledgment.

[0068] The method can additionally include sending 840 a subsequent
multicast/broadcast packet with a predetermined delay when the
acknowledgment is either a specific negative acknowledgment or a specific
affirmative acknowledgment. The method of FIG. 8 can also include
re-sending 850 the multicast/broadcast packet upon receiving a general
negative acknowledgment. The method can additionally include sending 860
the next packet without delay when the acknowledgment is a general
affirmative acknowledgment.

[0069]FIG. 9 illustrates a method according to an embodiment of the
present invention. The method includes receiving 910, at a cluster
member, either successfully or unsuccessfully, a multicast/broadcast
packet from a base station. Again, the term "receive" is not limited to
successful reception. The method also includes monitoring 920, at the
cluster member, to determine whether another cluster member responds to a
cluster head with a negative acknowledgment. If the packet was not
received correctly, the method can include sending 925 a negative
acknowledgment to the cluster head, using a D2D communication link. The
method further includes monitoring 930, at the cluster member, to
determine what kind of acknowledgment the cluster head uses to respond to
the base station, wherein the kind is one kind selected from a general
affirmative acknowledgment, a general negative acknowledgment, a specific
affirmative acknowledgment, or a specific negative acknowledgment.

[0070] The method can further include, when the cluster head did not
successfully receive the packet as indicated by a specific negative
acknowledgment and the cluster member successfully received the packet,
determining 940 whether to send the multicast/broadcast packet to the
cluster head and other cluster member(s) based on predetermined rules.
The predetermined rules include an order of priority among members of a
cluster, and wherein the cluster member determines whether to send the
multicast/broadcast packet based on the priority of the cluster member
relative to at least one other member of the cluster.

[0071]FIG. 10 illustrates a system according to certain embodiments of
the present invention. The system can include a first apparatus 1010,
which may be a cluster head. The system can further include a second
apparatus 1020, which may be a base station, such as an eNode B. The
system can also include one or more third apparatuses 1030 (two shown,
but more are possible), which may be cluster member devices.

[0072] Each of the first apparatus 1010, second apparatus 1020, and third
apparatus 1030 may include at least one memory 1040 including computer
program code 1050. Each of the first apparatus 1010, second apparatus
1020, and third apparatus 1030 can also include at least one processor
1060. The at least one memory 1040 and computer program code 1050 can be
configured, with the at least one processor 1060, to cause the
corresponding apparatus to perform a method, such as on of the methods
illustrated

[0073] The first apparatus 1010 and the third apparatus 1030 can be
connected to the second apparatus 1020 via a first wireless link 1070,
which may be a cellular link. The first apparatus 1010 and the third
apparatus 1030 can be connected to each other via a second wireless link
1080, which may be a D2D link.

[0074] One having ordinary skill in the art will readily understand that
the invention as discussed above may be practiced with steps in a
different order, and/or with hardware elements in configurations which
are different than those which disclosed. Therefore, although the
invention has been described based upon these preferred embodiments, it
would be apparent to those of skill in the art that certain
modifications, variations, and alternative constructions would be
apparent, while remaining within the spirit and scope of the invention.
In order to determine the metes and bounds of the invention, therefore,
reference should be made to the appended claims.